There have been a number of efforts at producing watercrafts that have the ability to accommodate passengers safely above the water as well as below the surface of the water. For the most part, watercraft seeking to achieve this objective from the past have not been commercially viable at any reasonable cost. Accordingly, the need remains for a commercially viable watercraft for both surface and submersible travel and accommodation of passengers. This invention addresses that need by providing a modular watercraft which can operate as a conventional speedboat while on the surface of the water, and as a submarine, when deployed for travel below the water surface.